Cooler for electronic equipment

ABSTRACT

[Object] A cooling device for a thin electronic equipment having a larger heat radiation area and preventing leakage of refrigerant. 
 
[Means for Solving Problems] A cooling device includes first and second cooling panels ( 1, 2 ) wherein a passage ( 11, 21 ) is formed by bonding together a top heat radiation panel and a bottom heat radiation panel each having a groove therein, and a circulation pump ( 3 ) for circulating refrigerant within the passage ( 11, 21 ). In the top heat radiation panel of the second cooling panel ( 2 ) are formed an outlet port through which the refrigerant flows out from the passage ( 21 ) to the circulation pump ( 3 ) and an inlet port through which the refrigerant flows in from the circulation pump ( 3 ) to the passage ( 21 ). The circulation pump ( 3 ) is fixed onto the top heat radiation plate of the cooling panel ( 2 ) so that the suction port and discharge port are aligned with the outlet port and inlet port, respectively.

TECHNICAL FIELD

The present invention relates to a cooling device for an electronicequipment and, more particularly, to a cooling device for an electronicequipment, suitable to cooling a heating part, such as a CPU, mounted ona notebook personal computer.

BACKGROUND ART

Along with the increase in the amount and speed of processing, heatingparts having a larger power dissipation, such as a CPU, are installed inthe recent electronic equipment, such as a personal computer, and theamount of heat generated by the heating parts is more and moreincreasing. In these electronic equipment, the variety of electronicparts used therein generally have an operating temperature limit due tothe temperature dependency of the heat-resistance reliability andoperating characteristic. Thus, it is an urgent subject to establish thetechnique for efficient radiation of the heat generated within theelectronic equipment toward the outside thereof.

In general, the electronic equipment, such as a personal computer,includes a metal heat sink or so-called heat pipe etc. attached to theCPU etc. as a heat absorbing part, which diffuses the heat across theentirety of the electronic equipment by heat conduction, or anelectromagnetic cooling fan attached onto the housing for radiating theheat from inside to outside of the electronic equipment.

For example, an electronic equipment, such as a notebook personalcomputer, on which electronic parts are densely mounted, has a smallheat radiation space within the electronic equipment, and is capable ofcooling a CPU having a power consumption of up to 300 watts by using aconventional cooling fan alone or a combination of the cooling fan andheat pipe. It is difficult, however, to sufficiently radiate theinternal heat from a CPU having a power consumption above that value.

Even if the heat radiation is possible, it is essential to install alarge blowing-capacity cooling fan, and if an electromagnetic coolingfan is used therefor in particular, silence is lost due to the noisesuch as a hissing sound by the rotary blades. In a personal computerused as a server, request for a smaller size and the silence isincreasing along with the spreading use thereof, and accordingly, thereoccurs a problem in the heat radiation therefrom similarly to thenotebook personal computer.

For efficient radiation of the increased amount of heat, use of aliquid-type cooling device which circulates refrigerant therethrough isstudied. For example, JP-A-2003-67087 describes a liquid-type coolingdevice, wherein a personal computer body is provided with aheat-receiving head which receives heat from the heating parts of thepersonal computer body. A housing is also disposed which is providedwith a connecting head, to which the heat from the heating parts istransferred through the heat-receiving head, a tube connected to theconnecting head and filled with refrigerant, and a pump for circulatingthe refrigerant, which are disposed on the bottom of the personalcomputer body.

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention

The conventional technique described in the above publication has theconfiguration wherein the refrigerant is circulated through the tubedisposed on the bottom of the personal computer body, an thus asufficient heat radiation area cannot be secured therein. Accordingly,there is a problem in that it only achieves a lower cooling efficientand it is difficult to achieve a smaller thickness for the coolingdevice.

The present invention is devised in view of the above problems, and itis an object of the present invention to provide a cooling device for anelectronic equipment, which is capable of assuring a sufficient heatradiation area to improve the cooling efficiency and capable of beingreduced in the thickness thereof.

Means for Solving the Problems

In order to achieve the above object, the present invention provides acooling device for an electronic equipment, including: a first coolingpanel wherein a first passage through which refrigerant circulates isformed; a second cooling panel wherein a second passage through whichthe refrigerant circulates is formed, the second cooling panel beingdisposed to oppose the first cooling panel; and a circulation pump forcirculating the refrigerant through the first passage and the secondpassage to thereby diffuse heat transferred to the first cooling paneland the second cooling panel.

Moreover, the present invention provides an electronic equipmentmounting thereon the above cooling device for electronic equipment.

EFFECTS OF THE INVENTION

In accordance with the cooling device for an electronic equipment of thepresent invention, arrangement of the first cooling panel and the secondcooling panel opposing each other and circulation of the refrigerant bythe circulation pump within the passage in these cooling panels providea cooling device having a sufficient heat radiation area and a highercooling efficiency.

It is preferable that the cooling device for electronic equipment of thepresent invention include a coupling member bearing the first coolingpanel and the second cooling panel for opening and closing with respectto each other. A compact-shaped cooling device can be obtained.

It is also preferable that at least one of the first cooling panel andthe second cooling panel include a micro-channel structure within thepassage, the micro-channel structure including a plurality of narrowpassages having a width smaller than the width of the passage. In thiscase, it is also preferable that the at least one of the first coolingpanel and the second cooling panel include an area in which anair-cooled fin is formed on a surface thereof, the area being disposeddownstream of the micro-channel structure. Moreover, it is alsopreferable that the passage in the area be wobbled. Furthermore, it isalso preferable that a cooling fan be disposed corresponding to theair-cooled fin.

It is preferable that the circulation pump be fixed onto the surface ofthe second cooling panel. It is also preferable that a reservoircommunicated with the second passage be disposed on a surface of thesecond cooling panel. In an alternative, a reservoir communicated withthe second passage be formed within the second cooling panel. It is alsopreferable that one or both of the first cooling panel and the secondcooling panel be formed by bonding together a top heat radiation paneland a bottom heat radiation panel, in at least one of which is formed agroove. It is preferable that the first cooling panel have an areasmaller than the area of the second cooling panel. Moreover, it ispreferable that the first passage have a width smaller than the width ofthe second passage and that the first passage have a depth larger thanthe depth of the second passage.

BRIEF DESCRIPTION OF HE DRAWINGS

[FIG. 1] (a) is a top plan view of a cooling device for an electronicequipment according to a first embodiment of the present invention, and(b) and (c) are a side view and a front view, respectively, thereof.

[FIG. 2] A top plan view showing the configuration of the passageunderlying the air-cooled fin shown in FIG. 1.

[FIG. 3] (a) is top plan view of the bottom heat radiation plate of thefirst cooling panel configuring the first cooling panel member shown inFIG. 1, and (b) is a side view thereof.

[FIG. 4] (a) is a top plan view of the top heat radiation plate of thefirst cooling panel configuring the first cooling panel member shown inFIG. 1, and (b) is a side view thereof.

[FIG. 5] A top plan view showing the configuration of the introductionportion for the micro-channel structure shown in FIG. 1.

[FIG. 6] (a) is a top plan view of the second cooling panel shown inFIG. 1, and (b) and (c) are a side view and a front view, respectively,thereof.

[FIG. 7] (a) is a top plan view of the bottom heat radiation plate ofthe second cooling panel configuring the second cooling panel membershown in FIG. 6, and (b) is a sectional view taken along line Y-Y′ shownin (a).

[FIG. 8] A top plan view showing the configuration of the top heatradiation plate of the second cooling panel configuring the secondcooling panel member shown in FIG. 6.

[FIG. 9] A graph showing the relationship between the width and depth ofthe passage shown in FIG. 6 and the cooling performance.

[FIG. 10] A graph showing the relationship between the width and platethickness of the passage shown in FIG. 6 and the resistance performanceto pressure.

[FIG. 11] (a) is an exploded perspective view of a first example of thecirculation pump shown in FIG. 1, and (b) is a side view in sectionthereof.

[FIG. 12] (a) and (b) are side views in section showing a mountingtechnique for the circulation pump shown in FIG. 11.

[FIG. 13] (a) is an exploded perspective view of a second example of thecirculation pump shown in FIG. 1, and (b) is a side view in sectionthereof.

[FIG. 14] (a) to (d) are side views in section showing a mountingtechnique for the circulation pump shown in FIG. 13.

[FIG. 15] (a) and (b) are side views in section showing a mountingtechnique for the circulation pump shown in FIG. 13.

[FIG. 16] (a) is an exploded perspective view of a third example of thecirculation pump shown in FIG. 1, and (b) is a side view in sectionthereof.

[FIG. 17] (a) to (d) are side views in section showing a mountingtechnique for the circulation pump shown in FIG. 16.

[FIG. 18] A perspective view showing the configuration of the reservoirshown in FIG. 1.

[FIG. 19] (a) and (b) are sectional views taken along line Z-Z′ in FIG.18.

[FIG. 20] (a) to (d) are explanatory views for showing the air storagefunction of the reservoir shown in FIG. 18.

[FIG. 21] (a) is a perspective view showing a first example ofassembling the cooling device for an electronic equipment according tothe present invention into the electronic equipment, and (b) is asectional view taken along line Z-Z′ in (a).

[FIG. 22] (a) is a perspective view showing a second example forassembling the cooling device for an electronic equipment according tothe present invention into the electronic equipment, and (b) is asectional view taken along line Z-Z′ in (a).

[FIG. 23] (a) is a perspective view showing a third example forassembling the cooling device for an electronic equipment according tothe present invention into the electronic equipment, and (b) is asectional view taken along line Z-Z′ in (a).

[FIG. 24] A top plan view showing an example of experiment for thecooling effect depending on the change of air-flow on the bottom surfaceof the second cooling panel shown in FIG. 1.

[FIG. 25] A graph showing the relationship between the change ofair-flow on the bottom surface of the second cooling panel shown in FIG.1 and the cooling effect.

[FIG. 26] A top plan view of the second cooling panel in a coolingdevice for an electronic equipment according to a second embodiment ofthe present invention.

[FIG. 27] (a) to (d) are top plan views showing the structure of thestanding-rest-type reservoir used in the second embodiment.

BEST MODES FOR CARRYING OUT THE INVENTION

Now, the present invention will be described in more detail based on theembodiments of the present invention with reference to the drawings.Similar constituent elements are designated by similar referencenumerals throughout the drawings.

Referring to FIG. 1, a cooling device for an electronic equipmentaccording to a first embodiment includes a first cooling panel 1, asecond cooling panel 2, and coupling members 61, 62, which coupletogether the first cooling panel 1 and second cooling panel 2, and bearthe first cooling panel 1 for allowing opening and closing movementthereof with respect to the second cooling panel 2 in the direction ofarrows shown in FIG. 1(c).

The cooling device has a function of cooling the heating parts 7, suchas CPU or other heating bodies generating heat, by circulatingrefrigerant such as water and antifreeze liquid through the passage,which is formed in the first cooling panel 1 and second cooling panel 2.The numeral 84 shown in FIG. 1 denotes a battery which is located thereupon mounting the cooling device on the electronic equipment, and thesecond cooling panel 2 has a shape that does not overlap the area forthe battery 84.

The shape of the first cooling panel 1 and second cooling panel 2 shownin FIG. 1 is suitably determined based on a variety of constraints, uponmounting the same on an electronic equipment.

A metallic material, such as copper (Cu) and aluminum (Al), having asuperior heat conductivity is used for the first cooling panel 1, inwhich the passage 11 and a micro-channel structure 12 are formed, asshown in FIG. 1. The top and bottom surfaces of the first cooling panel1 are provided with respective air-cooled fins 13, and the passage 11within the area 13A, in which the air-cooled fins 13 are formed, isconfigured as a wobbled passage 111 for improving the cooling effect, asshown in FIG. 2. The numeral 5 shown in FIG. 1(a) denotes a cooling fan5, which forms an air-flow in the air-cooled fin provided on the firstcooling panel 1, for improvement of air-cooling effect.

The first cooling panel 1 is manufactured by bonding the bottom heatradiation plate 17 and the top heat radiation plate 18 shown in FIGS. 3and 4, respectively, by using a bonding technique such as diffusionbonding, braze bonding or laser bonding. The groove 171 and the narrowgrooves 172 in the micro-channel structure 12, which are formed on thebottom heat radiation plate 17 of the first cooling panel, are coveredby the top heat radiation plate 18 of the first cooling panel, therebyforming the passage 11 and the micro-channel structure 12. The formationof the groove 171 and the narrow grooves 172 of the micro-channelstructure on the bottom heat radiation plate 17 of the first coolingpanel may be performed by pressing to form these grooves, by molding inthe state of having the grooves, or by grinding.

In the bottom heat radiation plate 17 of the first cooling panel areformed an opening B configuring an inlet port through which therefrigerant flows into the passage 11, and an opening C configuring anoutlet port through which the refrigerant flows out of the passage 11.The opening B and opening C are coupled to metallic tube 14 and metallictube 15, respectively. Flexible metallic tubes are used for the metallictubes 14, 15, to thereby incur no obstacle against the opening andclosing movement of the first cooling panel 1 with respect to the secondcooling panel 2.

The area in which the micro-channel structure 12 is formed on the bottomsurface of the bottom heat radiation plate 17 of the first cooling panelcontacts the top surface of the heating parts 7 such as CPU and otherheating bodies which have a large power dissipation and generate heatlocally in a small area. The heat generated by the heating parts 7 istransferred to the refrigerant flowing within the micro-channelstructure 12 via the bottom heat radiation plate 17 of the first coolingpanel. The micro-channel structure 12 includes a plurality ofnarrow-width channels having a width of 1 mm or smaller, which issmaller than the width of the passage 11 formed in the first coolingpanel 1. The micro-channel structure 12 is formed in the area in whichthe bottom heat radiation plate 17 of the first cooling panel contactsthe heating parts 7, and has a dimension larger than this area. In thefirst embodiment, the passage 11 formed in the first cooling panel 1 was6 mm wide and 1.5 mm deep, and 38 channels having a width of 0.5 mm anda depth of 1.5 mm were formed in the micro-channel structure 12.

The inlet through which the refrigerant flows into the micro-channelstructure 12 is such that the width of the passage 11 is graduallywidened toward the micro-channel structure 12 to be equal to the widthof the micro-channel structure 12 at the end thereof, as shown in FIG.5. The inlet of the micro-channel structure is provided with guideplates 16 for diffusing the refrigerant flowing from the passage 11 toflow in the width of the micro-channel structure 12. The guide plates 16includes first guides plates 161, second guide plates 162 and thirdguide plates 163, which are arranged consecutively from the upstream ofthe refrigerant and each forms a pair located on left and right sides.The relationship between the lengths of the guide plates is such that aguide plate located at the upstream side is longer than another, i.e.,the first guide plates 161 are longer than the second guide plates 162,which are longer than the third guide plates 163. The relationshipbetween angles θ of guide plates, shown in FIG. 5, with respect to theflow direction of the refrigerant is such that the angle of a guideplate located at the upstream side is larger than the angle of another,i.e., angle of the first guide plates 161 is larger than the angle ofthe second guide plates 162, which is larger than the angle of the thirdguide plates 163.

A metallic material, such as copper (Cu) and aluminum (Al), having asuperior heat conductivity is used for the second cooling panel 2, whichis provided with a passage 21 therein, and provided with a circulationpump 3 and a reservoir 4 attached on the top surface thereof, as shownin FIG. 6.

The second cooling panel 2 is such that a bottom heat radiation plate 23and a top heat radiation plate 24 shown in FIGS. 7 and 8, respectively,are bonded together by using a bonding technique such as diffusionbonding, braze bonding or laser bonding. A groove 231 formed on thebottom heat radiation plate 23 of the second cooling panel is covered bythe top heat radiation plate 24, to thereby form the passage 21. Theformation of the groove 231 on the bottom heat radiation plate 23 of thesecond cooling panel 2 may be performed by pressing to form the groove231, by molding in the state of having the groove 231, or by grinding toform the groove 231. Further, the groove may be formed on the top heatradiation plate 24, or may be formed on both the top heat radiationplate 23 and bottom heat radiation plate 24.

The central portion of the passage 21 of the second cooling panel 2,i.e., the central portion of the groove 231 formed on the bottom heatradiation plate 23 of the second cooling panel is provided with aplurality of struts 22 arranged at a constant pitch. The struts 22assure the strength during bonding together the bottom heat radiationplate 23 and top heat radiation plate of the second cooling panel 2. Therelationship between the width and depth of the passage 21 and thecooling performance is such that a larger width or a smaller depth ofthe passage improves the cooling performance as shown in FIG. 9.However, a smaller width of the passage or a smaller plate thicknessreduces the withstand-pressure performance, as shown in FIG. 10.Accordingly, the passage 21 is required to have a larger width and asmaller depth in the view point of the cooling performance, whichreduces the withstand-pressure performance however. Thus, in the firstembodiment, the object of the struts 22 is to improve thewithstand-pressure performance. Although the struts 22 are formed at thecentral portion of the passage 21 in the first embodiment, the locationof the struts 22 is not limited to the central portion, and the strutsmay be arranged in a lattice or zigzag fashion, for example. In thefirst embodiment, the passage 21 formed in the second cooling panel 2was 20 mm wide and 0.8 mm deep, and the struts 22 having a width of 0.5mm and a length of 2 mm were formed at a 20 mm pitch in the centralportion of the passage 21.

The top heat radiation plate 24 of the second cooling panel is providedwith an opening (branch hole) 25 communicated with the reservoir 4, arefrigerant outlet port 26 through which the refrigerant flows out ofthe passage 21 toward the circulation pump 3, a refrigerant inlet port27 through which the refrigerant flows in from the circulation pump 3toward the passage 21, an opening A configuring an outlet port throughwhich the refrigerant flows out of the passage 21, and an opening Dconfiguring an inlet port through which the refrigerant flows into thepassage 21. The opening A and opening D are coupled to metallic tube 14and metallic tube 15, respectively. A micro-channel structure may beformed in the second cooling panel 2.

Hereinafter, the flow of the refrigerant in the first embodiment will bedescribed in detail.

The refrigerant discharged from the circular pump 3 provided on the topsurface of the second cooling panel 2 passes through the refrigerantinlet port 27 to the passage 21 formed in the second cooling panel 2,and flows into the first cooling panel 1 via the opening A, metallictube 14 and opening B. The refrigerant flowing into the first coolingpanel 1 passes through the passage 11 formed in the first cooling panel1 to flow into the micro-channel structure 12.

The refrigerant flowing into the micro-channel structure 12 absorbs theheat generated by the heating parts 7, passes through the wobbledpassage 111 formed in the area in which the air-cooled fins 13 areprovided, to flow into the second cooling panel 2 via the opening C,metallic tube 15 and opening D. The refrigerant flowing into the secondcooling panel 2 passes through the passage 21 formed in the secondcooling panel 2, reaches the refrigerant outlet port 26 after passingunderneath the opening 25 communicated with the reservoir 4, and againflows into the circulation pump 3.

By circulating the refrigerant by using the circulation pump 3, asdescribed above, the heat generated by the heating parts 7 is diffusedby heat conduction over the entirety of the first cooling panel 1 andsecond cooling panel 2, thereby improving the heat radiation effect.

Next, a first configuration example of the circulation pump 3 which isattached to the top heat radiation plate 24 of the second cooling panel2 at the top side thereof will be described in detail with reference toFIGS. 11 and 12.

FIG. 11 illustrates the first configuration example of the circulationpump shown in FIG. 1, wherein (a) is an exploded perspective view, and(b) is a side view in section thereof. FIG. 12 is a side view in sectionshowing the mounting process for the circulation pump illustrated inFIG. 11.

Referring to FIG. 11, the first configuration example of the circularpump 3 includes a pump housing 311, an O-ring 312 made of rubber resin,a piezoelectric vibration plate 313, a top plate 314 for pressing thepiezoelectric vibration plate 313. The pump housing 311 is provided witha suction port 315 and a discharge port 316 which oppose the refrigerantoutlet port 26 and refrigerant inlet port 27, respectively, formed onthe top heat radiation plate 24 of the second cooling panel, and definestherein a space configuring a pump chamber 319. The suction port 315 isprovided with an inlet check valve 317 which prevents a back-flow fromthe pump chamber 319 to the passage 21, whereas the discharge port 316is provided with an outlet check valve 318 which prevents a back-flowfrom the passage 21 to the pump chamber 319. The inlet check valve 317and outlet check valve 318 are configured each by a thin metallic reedvalve, and coupled to the bottom surface of the pump housing 311 byusing spot welding or screws.

The piezoelectric vibration plate 313 is a piezoelectric-bendedvibration plate used as a driving source of the circulation pump 3, isconfigured by bonding together a piezoelectric element and an elasticplate, and is subjected to liquid-tight molding so that thepiezoelectric element does not directly contact the refrigerant liquid.Piezoelectric ceramic or piezoelectric single crystal may be used forthe piezoelectric element. A thin metallic plate such as made of copperalloy e.g., bronze phosphate or stainless alloy, or a thin carbon fiberplate or resin plate such as PET plate may be used as the elastic plate.The detailed structure of the piezoelectric vibration plate 313 may be auni-morph, bimorph etc., or otherwise a layered structure includinglayered piezoelectric elements.

Referring to FIG. 12(a), the mounting process for the circulation pumpshown in FIG. 11 includes the first step of bonding the pump housing 311onto the top heat radiation plate 24 of the second cooling panel to forman integral body for fixing together, by using a bonding technique suchas diffusion bonding, braze bonding or laser bonding. In this step, thesuction port 315, discharge port 316, space for the pump chamber 319,inlet check valve 317 and outlet check valve 318 are formed and bondedin/to the pump housing 311.

Thereafter, as shown in FIG. 12(b), the O-ring 312 is inserted, and thepiezoelectric vibration plate 313 is mounted thereon, to therebyconfigure the pump chamber 319. Then, the O-ring 312 is firmlycompressed and closely contacted by using the top plate 314 for assuringthe liquid-tight and for allowing the piezoelectric vibration plate 313to be fixed at the periphery thereof. In this step, the top plate 314may be fixed with screws from the top or may be fastened after providingthe periphery of the top plate 314 with screws.

As described above, in the first configuration example of thecirculation pump 3, the circulation pump 3 and the second cooling panel2 are coupled together using a metallic bonding technique to form aperfect integral body, thereby preventing the pressure loss, leakage ofliquid etc. In addition, the structure of the integral body of thecirculation pump 3 and second cooling panel 2 allows smaller thicknessand lower cost thereof. Use of this structure for the circulation pump 3achieves a smaller-thickness cooling device having a height as small as7 mm or smaller at the maximum portion at which the circulation pump 3is arranged.

Thereafter, a second configuration example of the circulation pump 3which is attached to the top heat radiation plate 24 of the secondcooling panel 2 at the top side thereof will be described in detail withreference to FIGS. 13 through 15.

FIG. 13 shows the second configuration example of the circulation pumpshown in FIG. 1, wherein (a) is an exploded perspective view, and (b) isa side view in section thereof. FIGS. 14 and 15 are side view in sectionshowing the mounting process for the circulation pump illustrated inFIG. 13.

Referring to FIG. 13, the second configuration example of thecirculation pump 3 is comprised of a pump housing 231, acheck-valve-formed circular plate 322, an O-ring made 312 of rubberresin, a piezoelectric vibration plate 313, and a top plate 314 forpressing the piezoelectric vibration plate 313. The check-valve-formedcircular plate 322 is provided with a suction port 315 and a dischargeport 316 formed so as to oppose the refrigerant outlet port 26 andrefrigerant inlet port 27, respectively, formed in the top heatradiation plate 24 of the second cooling panel. The suction port 315 isprovided with an inlet check valve 317 for preventing the back-flow fromthe pump chamber 319 to the passage 21, whereas the discharge port 316is provided with an inlet check valve 318 for preventing the back-flowfrom the passage 21 to the pump chamber 319. The inlet check valve 317and outlet check valve 318 are configured each by a thin metallic reedvalve, and coupled to the check-valve-formed circular plate 322 by usingspot welding or screws.

Referring to FIGS. 14(a) to 14(c), the mounting process for the circularpump 3 shown in FIG. 13 includes the first step of bonding the pumphousing 321 onto the top heat radiation plate 24 of the second coolingpanel by using a bonding technique, such as diffusion bonding, brazeboding or laser welding, to form an integral body. In the pump housing603, a portion to be configured as the pump chamber 319 may be formedprior to or subsequent to this step.

Thereafter, as shown in FIG. 14(d), the check-valve-formed circularplate 322 in/to which the suction port 315, discharge port 316, inletcheck valve 317 and outlet check valve 318 are formed and bonded isinserted within the pump housing 321.

Thereafter, as shown in FIG. 15(a), the O-ring 312 is inserted, and thepiezoelectric vibration plate 313 is mounted thereon, as shown in FIG.15(b), thereby configuring the pump chamber 319. Subsequently, theO-ring 312 is firmly compressed and closely contacted by using the topplate 314 for assuring the liquid-tight and for allowing thepiezoelectric vibration plate 313 to be fixed at the periphery thereof.In this step, the top plate 314 may be fixed with screws from the top,or may be fastened after providing the periphery of the top plate withscrews.

As described above, in the second configuration example of thecirculation pump 3, the suction port 315, discharge port 316, inletcheck valve 317 and outlet check valve 318 are formed in and bonded ontothe check-valve-formed circular plate 322 in advance, whereby thecheck-valve-formed circular plate 322 can be replaced as a whole. Inthis configuration, if the pump performance is degraded due to theclogging of the suction port 315 or discharge port 316 or due to plasticdeformation of the inlet check valve 317 or outlet check valve 318 aftera long-term service, it is sufficient that the check-valve-formedcircular plate 322 be replaced to recover the pump performance, therebyallowing an easy maintenance.

Thereafter, a third configuration example of the circulation pump 3attached to the top heat radiation plate 24 of the second cooling panelon the top surface thereof will be described in detail with reference toFIGS. 16 and 17. FIG. 16 illustrates the third configuration example ofthe circular pump 3 shown in FIG. 1, wherein (a) is an explodedperspective view and (b) is a side view in section thereof. FIG. 17 is aside view in section showing a mounting process for the circulation pumpillustrated in FIG. 16.

Referring to FIG. 16, the third configuration example of the circulationpump 3 is comprised of a pump housing 331, a check-valve-formed circularplate 322, an O-ring 312 made of rubber resin, a piezoelectric vibrationplate 313 and a top plate 314 for pressing the piezoelectric vibrationplate 313. The bottom surface of the pump housing 331 is provided with apump-bottom-surface inlet port 333 and a pump-bottom-surface outlet port334, which are formed so as to oppose the refrigerant outlet port 26 andrefrigerant inlet port 27, respectively, formed in the top heatradiation plate 24 of the second cooling panel.

The pump-bottom-surface inlet port 333 and pump-bottom-surface outletport 334 are coupled to the suction port 315 and discharge port 316,respectively, of the check-valve-formed circular plate 322. The suctionport 315 is provided with an inlet check valve 317 for preventing theback-flow from the pump chamber 319 to the passage 21, whereas thedischarge port 316 is provided with an outlet check valve 318 forpreventing the back-flow from the passage 21 to the pump chamber 319.The inlet check valve 317 and outlet check valve 318 are configured eachby a thin metallic reed valve, and coupled to the check-valve-formedcircular plate 322 by using spot welding or screws.

Referring to FIGS. 17(a) and 17(b), the mounting process for thecirculation pump 3 shown in FIG. 16 includes the first step of bondingtogether the second-cooling-panel top heat radiation plate 24 and thesecond-cooling-panel bottom heat radiation plate by using a metallicbonding technique, such as diffusion bonding, braze bonding or laserbonding, to thereby form an integral body.

Thereafter, the check-valve-formed circular plate 322 in/to which thesuction port 315, discharge port 316, inlet check valve 317 and outletcheck valve 318 are formed and bonded is inserted within the pumphousing 331. Subsequently, the O-ring 312 is inserted, the piezoelectricvibration plate 313 is mounted thereon, and the O-ring 312 is firmlycompressed and closely contacted by using the top plate 314 for assuringthe liquid-tight and for fixing the piezoelectric vibration plate 313 atthe periphery thereof, thereby installing the circulation pump 3 inadvance. In this step, the top plate 314 may be fixed with screws fromthe top, or may be fastened after providing the periphery of the topplate with screws.

Thereafter, as shown in FIG. 17(c), O-rings 332 are inserted in O-ringgrooves 335 formed on the bottom surface of the pump so as to isolatethe pump-bottom-surface inlet port 333 from the pump-bottom-surfaceoutlet port 334, followed by fastening together the circulation pump 3and the second cooling panel 2 with screws to finish the mounting.

As described above, in the third configuration example of thecirculation pump 3, an easy maintenance such as by replacement of thecirculation pump 3 for dealing with degradation in the performance ofthe circular pump 3 can be obtained, while achieving a lower cost. Thebonding of the circular pump 3 and the second cooling panel 2 assuresthe liquid-tight to a sufficient extent, although not so high extent asachieved by the metallic bonding used in the first and secondconfiguration examples.

Next, the configuration of the reservoir 4 attached onto the top heatradiation plate 24 of the second cooling panel at the top surfacethereof will be described in detail with reference to FIGS. 18 to 20.

FIG. 18 is a perspective view showing the configuration of the reservoirshown in FIG. 1, FIG. 19 is a sectional view taken along line Z-Z′ inFIG. 18, and FIG. 20 is an explanatory view for describing the airstorage function of the reservoir shown in FIG. 18.

The reservoir 4 is a laid-down-type reservoir of a hollow disk, as shownin FIG. 6, and fixed onto the top heat radiation plate 24 to overlie thepassage 21 at the upstream side of the circulation pump 3 (upstream ofthe inlet of the refrigerant into the circulation pump 3). Referring toFIGS. 18 and 19, the reservoir is arranged so that the branch hole 43provided in the bottom surface of the reservoir 4 is aligned with theopening 25 formed in the top heat radiation plate 24 of the secondcooling panel. The branch hole 43 communicated with the reservoir 4 hasa smaller cross-sectional area compared to the passage 21 to therebyincrease the acoustic impedance and thus minimizes the inlet flow rateof the refrigerant into the reservoir 4 without impeding the flow of therefrigerant through the passage 21.

Since the reservoir 4 having the branch hole 43 is coupled to thepassage 21 at the top side thereof, air bubbles appearing in the passage21 due to a temperature change etc. are trapped by the overlyingreservoir 4 through the opening 25 formed in the top radiation plate 24of the second cooling panel. The air 45 trapped enters the reservoir 4through the branch hole 43. If the air stops in the vicinity of the exitof the branch hole 43, other air 45 subsequently trapped cannot enterthe reservoir 4. In view of this, a protrusion 42 is formed on the capof the reservoir 4 at a position overlying the exit of the branch hole43 so as not to allow the air to stop at the vicinity of the exit of thebranch hole 43. The protrusion 42 diffuses the air 45 exiting throughthe exit of the branch hole 43 toward the periphery thereof. Theprotrusion 42, if formed as a conical shape, can effectively prevent thedetention of air. The configuration, wherein the protrusion 42 has adownwardly convex portion and the convex portion has an area smallerthan the area of the branch hole, achieves the prevention of thedetention of air 45.

The air 45 trapped in the reservoir 4 acts for alleviating the pressurechange in the passage 21 caused by expansion and compression of theliquid due to a temperature change, thereby contributing an improvementin the decay endurance of the cooling device. On the other hand, if theair 45 trapped enters the passage 21 to flow into the circulation pump,there arises a possibility that the discharge pressure of thecirculation pump 3 is reduced to degrade the performance of thecirculation pump 3, whereby the flow rate of the refrigerant isconsiderably reduced. Thus, the bottom surface of the reservoir 4 isprovided with a taper portion 41 of a truncated conical shape having anapex at the exit of the branch hole 43, as shown in FIGS. 18 and 19. Thetaper portion 41 allows the air 45 trapped in the reservoir 4 to staytherein as much as possible, even if the cooling device is turned upsidedown. For the air trapped in the reservoir 4 not to return to thepassage, it is necessary that the exit of the branch hole 43 be immersedin the refrigerant at any time. In the first embodiment, the boundarysurface A-A′ at which the exit of the branch hole 43 is located isconfigured so that the volume of the reservoir 4 below the boundarysurface A-A′ is smaller than the volume of the reservoir above theboundary surface A-A′, whereby the reservoir 4 is filled with therefrigerant 44 so that the liquid level of the refrigerant 44 is locatedin the reservoir 4 above the boundary surface A-A′, as shown in FIG.19(b).

The normal state in which the cooling device of the first embodiment isused is such that shown in FIG. 20(a), wherein the air 45 stays in theupward position because the air 45 has a lower specific density than therefrigerant 44. It is to be noted that the refrigerant 44 is filled inthe reservoir 4 so that the exit of the branch hole 43 (the apex of thetaper of the taper portion 41) is located within the liquid. Inaddition, the volume of the reservoir 4 is designed to have a sufficientvolume for endurance in consideration of the amount of heat expansion ofthe refrigerant 44 as well as the heat expansion and withstand pressureof the reservoir 4.

If the cooling device is inclined into a slanted state in the nextstage, the reservoir 4 assumes the posture shown in FIG. 20(b), whereinthe air 45 in the reservoir 4 stays to be deviated in a specificdirection. In this state either, the exit of the branch hole 43 does notstay away from the liquid, whereby the air 45 in the reservoir 4 doesnot enter the branch hole 43.

If the cooling device is further inclined to be turned upside down inthe next stage, the reservoir 4 assumes the posture shown in FIG. 20(c).In this state either, the refrigerant 44 is filled at above the boundarysurface A-A′, due to the configuration wherein the bottom surface of thereservoir 4 is provided with the taper portion 41 and thus the volume ofthe reservoir 4 below the boundary surface A-A′ shown in FIG. 20 islarger than that above the boundary surface. Thus, the exit of thebranch hole 43 is immersed in the refrigerant 44 at any time so that theair 45 remains to stay in the reservoir 4 and does not enter the branchhole 43.

If the cooling device is further inclined in the next stage, thereservoir 4 shifts from the posture shown in FIG. 20(c) to the postureshown in FIG. 20(d), whereby the air 45 in the reservoir 4 rises on thetaper surface of the taper portion 41. After the air 45 reaches thevicinity of the exit of the branch hole 43, it stays in the oppositelocation. In this state, the cross-sectional area of the branch hole 43is extremely small so that the air 45 passes over the branch hole 43 tothereby stay in the opposite location.

For verification of the effectiveness of the reservoir 4 in the firstembodiment, a prototype cooling device including a branch hole having a2-mm diameter and a reservoir 4 having a 50-mm diameter and a 7-mmheight (taper portion 41 having a 4-mm vertical interval) wasmanufactured. This cooling device was coupled to a commerciallyavailable high-pressure pump for conducting a withstand-pressure test,wherein a pressure having an amplitude of 0 to 1 MPa and a frequency of10 Hz was applied in an assumption of a steep temperature change beingapplied to the electronic equipment.

In the results of the test, without the reservoir 4, an instant leakagewas observed at a pressure of 200 kPa (twice the normal pressure) due topeel-off in the bottom wall and passage plate, whereas the leakage wasnot observed in case of provision of the reservoir 4 up to a pressure of1 MPa (10 normal pressures) and a frequency of 150000 cycles, whereby animprovement in the withstand-pressure performance of the reservoir 4 wasassured in the first embodiment.

As described above, the reservoir 4 in the first embodiment has anadvantage in that the reservoir can be arranged two-dimensionally for aportion or the entirety of the passage 21 extending in a two-dimensionalplane, whereby a small thickness can be achieved. It is to be noted thatthis type of the reservoir 4 can be provided in a plurality thereof forachieving a larger advantage over a single one. If the reservoir 4 isdetachably provided, there is a larger advantage in that the refrigerantis replenished if the amount of refrigerant should be reduced in thecooling device.

Next, examples of assembly of the cooling device of the first embodimentinto an electronic equipment will be described in detail with referenceto FIGS. 21 to 25.

FIG. 21 illustrates a first example of assembly into the electronicequipment, wherein (a) is a perspective view thereof and (b) is asectional view taken along line Z-Z′ shown in (a). FIG. 22 illustrates asecond example of assembly into the electronic equipment, wherein (a) isa perspective view thereof and (b) is a sectional view taken along lineZ-Z′ shown in (a). FIG. 23 illustrates a third example of assembly intothe electronic equipment, wherein (a) is a perspective view thereof and(b) is a sectional view taken along line Z-Z′ shown in (a). FIG. 24illustrates an example of the test for assuring the cooling effectduring the change in the amount of air flow on the bottom surface of thesecond cooling panel shown in FIG. 1. FIG. 25 shows the relationshipbetween the change in the amount of air flow on the bottom surface ofthe second cooling panel shown in FIG. 1 and the cooling effect.

Referring to FIG. 21, in the first assembly example, the housing 80 of anotebook personal computer having a typical thickness of around 3-4 cmis provided therein with main electric components having relativelylarge sizes and different thicknesses, such as DVD-RAM 81, FD-RAM 82,HDD 83, battery 84 and memory card 85, and a mother board 86 on which aheating part 7 such as CPU is provided. The second cooling panel 2 ismounted to underlie the mother board 86. In the first assembly example,it is assumed that the micro-channel structure 12 is formed in thesecond cooling panel 2, and the heating part 7 mounted on the topsurface of the mother board 86 is in contact with the top surface of thesecond cooling panel 2 in the area in which the micro-channel structure12 is formed.

The second assembly example has a higher cooling efficiency over thefirst assembly example. Referring to FIG. 22, the first cooling panel 1is mounted overlying the mother board 86 on which the heating part 7such as CPU is mounted, and the second cooling panel 2 is mountedunderlying the mother board 86. The heating part 7 mounted on the topsurface of the mother board 86 is in contact with the bottom surface ofthe first cooling panel 1 in the area in which the micro-channelstructure 12 is formed. The first cooling panel 1 can be opened andclosed, as described before. In the second assembly example, the openingmovement of the first cooling panel 1 allows an easy maintenance such asreplacement of the heating part 7 mounted on the top surface of themother board 86.

The third assembly example has a higher cooling efficiency over thesecond assembly example. Referring to FIG. 23, the first cooling panel 1is mounted overlying the mother board 86 on which the heating part 7such as CPU is mounted, and the second cooling panel 2 is mountedunderlying the mother board 86. The heating part 7 mounted on the topsurface of the mother board 86 is in contact with the bottom surface ofthe first cooling panel 1 in the area in which the micro-channelstructure 12 is formed. The first cooling panel 1 is provided with anair-cooled fin 13. There are provided a fan 5 which supplies an air flowonto the air-cooled fin 13 formed on the first cooling panel 1, and afan 51 which forms an air flow on the bottom surface of the secondcooling panel 2.

For verification of the relationship between the amount of air flowsupplied on the bottom surface of the second cooling panel 2 and thecooling effect in the third assembly example, as shown in FIG. 24, fans51 to 55 for forming the air flow on the bottom surface of the secondcooling panel 2 were arranged, wherein the heat resistance was measuredwhile changing the number of fans 51 to 55. The fan 5 which provided theair flow to the air-cooled fin 13 formed on the first cooling panel 1was operated at any time during the measurement. The results are suchthat, as shown in FIG. 25, a larger number of fans 51 to 55 provided areduced heat resistance, to thereby prove the improvement in the coolingeffect.

The heat resistance was also measured while changing the number of fans51 to 55, for another example wherein the air-cooled fin is formed onthe bottom surface of the second cooling panel 2. The results are suchthat, as shown in FIG. 25, there was substantially no difference in thecooling effect between the case where the air-cooled fin was formed onthe bottom of the second cooling panel 2 and the other case where therewas no air-cooled fin.

As described above, the first embodiment is configured such that thesecond cooling panel 2, wherein the passage 21 is formed by covering thegroove 213 formed on the bottom heat radiation plate 23 with the topradiation plate 24, is mounted on the bottom of the electronicequipment. This assures a sufficient heat radiation area to therebyimprove the cooling efficiency, and provides a smaller thickness for thecooling device. Even the smaller thickness of the cooling device resultsin effective prevention of the leakage of the refrigerant.

In addition, the first embodiment employs the configuration wherein thestruts for reinforcing the bonding between the bottom heat radiationplate 23 and the top heat radiation plate 24 are formed in the passage21 of the second cooling panel 2 mounted on the bottom of the electronicequipment. This allows a larger width for the passage 21 of the secondcooling panel 2 and a smaller thickness for the bottom heat radiationplate 23 and top heat radiation plate 24, thereby assuring a sufficientheat radiation area to improve the cooling efficiency and allowing asmaller thickness for the cooling device.

Moreover, the configuration wherein the circulation pump 3 is fixed ontothe top surface of the second cooling panel 2 mounted on the bottom ofthe electronic equipment in the first embodiment provides an effectiveprevention of the leakage of the refrigerant.

Moreover, the configuration, wherein the branch hole is provided whichbranches upward from the passage 21 of the second cooling panel 2mounted on the bottom of the electronic equipment in the firstembodiment and wherein the reservoir 4 is provided overlying the branchhole, allows the air bubbles generated due to the temperature changewithin the electronic equipment or the pressure change in the passage tobe trapped in the reservoir 4. This allows prevention of reduction inthe amount of outlet flow from the circulation pump 3 caused by mixingof air bubbles.

Moreover, the configuration, wherein the branch hole is provided whichbranches upward from the passage 21 of the second cooling panel 2mounted on the bottom of the electronic equipment in the firstembodiment and wherein the reservoir 4 is provided overlying the branchhole, allows the air 45 in the reservoir 4 to alleviate the pressurechange in the passage caused by the temperature change within theelectronic equipment. This allows prevention of damage due to the stressgenerating locally due to the pressure change in the passage.

Moreover, the first embodiment is such that the metallic material havinga superior heat conductivity is used for the bottom heat radiation plate23 and top heat radiation plate 24 of the second cooling panel 2configuring the passage 21 through which the refrigerant circulates andthat the top heat radiation plate 24 and the circulation pump 3 arecoupled together by a metallic bonding technique. This provides anintegral body for the circulation pump 3 and the passage 11, and allowsthe entirety of the passage 11 to be covered with the metallic material,thereby achieving the advantage of occurring of no evaporation orleakage of the refrigerant. It is to be noted that the structure (thirdconfiguration example) wherein the circulation pump 3 is coupled to thetop heat radiation plate 24 of the second cooling panel 2 via the O-ring332 may incur the possibility of occurring of evaporation or leakage ofthe refrigerant through the coupling by the O-ring 332 because of theseparate structure of the circulation pump 3. However, this case allowsan easy maintenance.

As described above, in the cooling device for an electronic equipmentaccording to the first embodiment of the present invention, the secondcooling panel, wherein the groove formed on the bottom heat radiationplate of the second cooling panel is covered with the top heat radiationplate of the second cooling panel, is mounted on the bottom of theelectronic equipment. This configuration assures a sufficient coolingarea to thereby improve the cooling efficiency, reduces the thickness ofthe cooling device, and prevents leakage of the refrigerant as much aspossible even in this small thickness of the cooling device.

Moreover, in the cooling device for an electronic equipment according tothe first embodiment of the present invention, struts for reinforcingthe bonding between the bottom heat radiation plate and the top heatradiation plate are formed in the passage of the second cooling panelmounted on the bottom of the electronic equipment. This configurationprovides a larger width for the passage of the second cooling panel, andreduces the thickness of the bottom heat radiation plate and top heatradiation plate of the second cooling panel. This assures a sufficientheat radiation area to thereby improve the radiation efficiency, andreduces the thickness of the cooling device.

Moreover, in the cooling device for an electronic equipment according tothe first embodiment of the present invention, the configuration,wherein the circulation pump is fixed onto the top surface of the secondcooling panel mounted on the bottom of the electronic equipment,effectively prevents leakage of the refrigerant.

Moreover, in the cooling device for an electronic equipment according tothe first embodiment of the present invention, the branch hole isprovided which branches upward from the passage of the second coolingpanel mounted on the bottom of the electronic equipment, and thereservoir is located overlying the branch hole. This allows the airbubbles generated due to the temperature change within the electronicequipment or the pressure change in the passage to be trapped in thereservoir, thereby effectively preventing the reduction in the amount ofoutlet flow from the circulation pump due to the mixing of the airbubbles.

Moreover, in the cooling device for an electronic equipment according tothe first embodiment of the present invention, the branch hole isprovided which branches upward from the passage of the second coolingpanel mounted on the bottom of the electronic equipment, and thereservoir is located overlying the branch hole. This allows the air inthe reservoir to alleviate the pressure change in the passage caused bythe temperature change in the electronic equipment, thereby effectivelypreventing the damage caused by the stress occurring locally due to thepressure change in the passage.

Moreover, in the cooling device for an electronic equipment according tothe first embodiment of the present invention, the metallic materialhaving a superior heat conductivity is employed for the bottom heatradiation plate and top heat radiation plate of the second cooling panelconfiguring the passage through which the refrigerant circulates, andthe top heat radiation plate of the second cooling panel and thecirculation pump are coupled together by using a metallic bondingtechnique. This provides an integral body for the circulation pump andthe passage, and allows the entirety of the passage to be covered withthe metallic material, thereby achieving the advantage of occurring ofno evaporation or leakage of the refrigerant. It is to be noted that thestructure wherein the circulation pump 3 is coupled to the top heatradiation plate of the second cooling panel via the O-ring may incur thepossibility of occurring of evaporation or leakage of the refrigerantbecause of the separate structure of the circulation pump 3.

Next, a cooling device for an electronic equipment according to a secondembodiment of the present invention will be described. With reference toFIG. 26 first, the simple structure of a standing-rest-type reservoir411 will be described. In the cooling device shown in the same drawing,the cooling panel (substrate) 20 has an integral body and includestherein a groove 231 configuring the passage 21. In addition, thepassage 21 extending in a two-dimensional plane is provided with alaid-down-type reservoir 4 and the standing-rest-type reservoir 411along the passage. Thus, the present cooling device can be used in astanding posture, for example, with the top side shown in FIG. 26 beingthe upside in the vertical direction and the bottom side shown in FIG.26 being the downside in the vertical direction. The standing-rest-typereservoir 411 plays the roll for alleviating the pressure change in thepassage against the expansion or compression caused by the temperaturechange of the refrigerant, and for trapping the air bubbles in thepassage 11.

On the other hand, if the device is used in the state where the shape ofFIG. 26 is a vertical view, i.e., the present cooling device is used aslaid down on a desk, the laid-down-type reservoir 4 plays the rollsimilar to that of the standing-rest-type reservoir 411. As describedabove, provision of both the reservoirs 4 and 411 allows the pressurechange caused by expansion or compression due to the temperature changeof the refrigerant in the passage to be alleviated in the case where theelectronic equipment body such as a notebook PC is used on a desk orused while being hanged on the wall, contributing improvement in thewithstand-pressure performance of the present cooling device by trappingthe air bubbles in the passage 21.

With reference to FIG. 27, the concrete configuration of thestanding-rest-type reservoir 411 will be described. FIG. 27 (a) to 27(c)show enlarged standing-rest-type reservoir 411 shown in FIG. 1, whereinthe electronic equipment body such as notebook PC is used in a standingposture. In other words, this figure is depicted in the state whereinthe user observes from the front thereof.

When the air bubbles 413 generated as by the temperature change andincluded in the refrigerant 415 circulated by the circulation pump 3within the passage 11 reach the vicinity of the standing-rest-typereservoir 411, the air bubbles 413 are introduced into thestanding-rest-type reservoir 411 along the wall surface of the taperportion 412 due to a lower specific density thereof compared to theliquid. After staying in the upper portion of the reservoir, the airbubbles 413 are eventually trapped in the air layer 414.

As the configuration for allowing the air bubbles 413 introduced withinthe standing-rest-type reservoir 411 not to return to the passage 11,the inlet portion of the standing-rest-type reservoir 411 is providedwith a trapezoid taper 412, wherein the inside of the standing-rest-typereservoir 411 is either wide in the lateral direction or longer in thevertical direction to have an internal volume at least comparable to orlarger than that of the laid-down-type reservoir 4.

Due to the configuration as described above, the air bubbles 413 do notreturn from the standing-rest-type reservoir 411 to the liquid in thepassage 11 so long as the configuration wherein the air bubbles 413 havethe specific density lower than that of the liquid satisfies. This factwas assured by the present inventors using experiments. Moreover,according to an example of the present invention, it was confirmed thatthe configuration wherein the standing-rest-type reservoir 411 had avolume comparable to or larger than the volume of the laid-down-typereservoir 4, or an optimization of the amount of the air layer 414within the reservoir alleviated the pressure change in the passagecaused by the expansion or compression of the refrigerant due to thetemperature change thereof.

Next, the shape of the standing-rest-type reservoir 411 will bedescribed. The reservoirs 411 shown in FIGS. 27(a) to 27(c) each play aroll for trapping the air bubbles 413 and alleviating the pressure.However, if the location for mounting the heating part, such as CPU,circulation pump 3 and laid-down-type reservoir 4 is changed, theoptimum design for the passage 11 suffers from a variety of restrictionstherefrom. In accordance with the examples, the shapes of thestanding-rest-type reservoirs 411 shown in FIGS. 27(a) to 27(c) areselected depending on the layout of the large electronic parts in theelectronic equipment including heating part on the mother board, such asCPU, or HDD and DVD, thereby effectively achieving the improvement inthe cooling performance and smaller thickness.

The standing-rest-type reservoir 411 shown in FIG. 27(a) is a laterallyelongate type, wherein it is wide in the lateral direction and short inthe longitudinal direction, whereby it allows a smallest spacing betweenthe passage 11 and another passage adjacent thereto in the verticaldirection, while assuring the function of the reservoir. Thestanding-rest-type reservoir 411 shown in FIG. 27(b) is a longitudinallyelongate type, whereby it allows a smallest spacing between horizontallyadjacent passages 11. Thus, by taking advantage of the spacing betweenvertically adjacent passages 11, a larger volume can be assured tothereby further alleviate the pressure change.

In the standing-rest-type reservoir 411 shown in FIG. 27(c), a portionof the standing-rest-type reservoir 411 is coupled to the passage 11.This allows the reservoir to trap the air bubbles in a larger amountcompared to the reservoirs shown in FIGS. 27(a) and (b), if the flowrate of the refrigerant flowing through the passage 11 increases. Insuch a case, the reservoir is not filled with liquid in its full space,thereby allowing a specific amount of air layer 414 to be assured andsecure trapping of the air bubbles 413.

In either structure of the standing-rest-type reservoir in the secondembodiment, the air bubbles 413 occurring in the passage can beeffectively trapped. Thus, the standing-rest-type reservoir 411 havingan air storage function can be extended two-dimensionally for the liquidcirculation path in the present cooling device, and can be embeddedtogether with the passage between the top heat radiation panel and thebottom heat radiation panel of the first cooling panel made of ametallic material such as aluminum and copper having a superior heatconductivity. This reduces the total thickness of the plate of thecooling member down to 2 mm or smaller. It is apparent that a pluralityof the same type or different types of the standing-rest-type reservoir411 and laid-down-type reservoir 4 can be provided instead of a singleone, to achieve a superior advantage.

It will be apparent that the present invention is not limited to theabove embodiments and that the embodiments may be modified as desiredwithin the scope of the technical concept of the present invention. Forexample, the number, location, shape etc. of the above constituentmembers are not limited to the above embodiments and may be selected assuitable number, location and shape for implementation of the presentinvention.

1. A cooling device for an electronic equipment, comprising: a firstcooling panel wherein a first passage through which refrigerantcirculates is formed; a second cooling panel wherein a second passagethrough which said refrigerant circulates is formed, said formed, saidsecond cooling panel being disposed to oppose said first cooling panel;and a circulation pump for circulating said refrigerant through saidfirst passage and said second passage to thereby diffuse heattransferred to said first cooling panel and said second cooling panel,wherein: said first cooling panel and said second cooling panel sandwichtherebetween an electronic circuit substrate.
 2. The cooling device foran electronic equipment according to claim 1, further comprising acoupling member bearing said first cooling panel and said second coolingpanel for opening and closing with respect to each other, and saidconnecting member has a flexibility.
 3. The cooling device for anelectronic equipment according to claim 1, wherein at least one of saidfirst cooling panel and said second cooling panel includes amicro-channel structure within said passage, said micro-channelstructure including a plurality of narrow passages having a widthsmaller than a width of said passage.
 4. The cooling device for anelectronic equipment according to claim 1, wherein said at least one ofsaid first cooling panel and said second cooling panel includes an areain which an air-cooled fin is formed on a surface thereof, said areabeing disposed downstream of said micro-channel structure.
 5. Thecooling device for an electronic equipment according to claim 4, whereinsaid passage in said area is wobbled.
 6. The cooling device for anelectronic equipment according to claim 4, wherein a cooling fan isdisposed corresponding to said air-cooled fin.
 7. The cooling device foran electronic equipment according to claim 1, wherein said circulationpump is fixed onto a surface of said second cooling panel.
 8. Thecooling device for an electronic equipment according to claim 1, whereina reservoir communicated with said second passage is disposed on asurface of said second cooling panel.
 9. The cooling device for anelectronic equipment according to claim 1, wherein a reservoircommunicated with said second passage is formed within said secondcooling panel.
 10. The cooling device for an electronic equipmentaccording to claim 1, wherein at least one of said first cooling paneland said second cooling panel is formed by bonding together a top heatradiation panel and a bottom heat radiation panel, in at least one ofwhich is formed a groove.
 11. The cooling device for an electronicequipment according to claim 1, wherein said first cooling panel has anarea smaller than an area of said second cooling panel.
 12. The coolingdevice for an electronic equipment according to claim 1, wherein saidfirst passage has a width smaller than a width of said passage.
 13. Thecooling device for an electronic equipment according to claim 1, whereinsaid first passage has a depth larger than a depth of said secondpassage.
 14. An electronic equipment mounting thereon the cooling devicefor electronic equipment according to claim 1.